There was a police guy in uniform sat inside guarding the house whilst the family was asleep.
After he is attacked, if you look closely there is a wound to the side of his head. Whether he died or not, it's not said.
Was the cop killed?
I'm gonna say "no", based on three factors;
It's never mentioned again and the scene ends with the senior policeman tipping his hat and leaving. I can't imagine any set of circumstances where they'd allow the family to spend the night in a house where a murder had happened.
In the source novel, the cop (Kevin) isn't killed
But already Russel had jumped our cop, and there was a yell from Kevin and the sound of something slamming against the wall in the hall, and I was rolling out of bed, grabbing at the shotgun under it, rushing for the bedroom door.
I got out in the hall just in time to see our Vietnam vet, black belt policeman take a marvelous left hook on the chin that bounced him over his chair even as his hand was in mid-draw for his revolver. The sound of the punch and the way Kevin went down like a broken manikin told me he wouldn’t be getting up for a while.
Price and another officer got Kevin awake and onto the couch to look him over. “You need to work on your stepover toe-hold,” the officer told him.
“That old bastard is as strong as God,” Kevin said.
An ambulance was called out, and a doctor came and looked at Kevin and me and my family. He clucked some, applied a bandage or two and gave us an aspirin